Thigh School

To get leaner, stronger thighs, the leg-extension machine at the gym is an excellent choice—as long as the seat is set properly. In a study from the Journal of Sports and Conditioning Research, 20 people performed eight repetitions on the quadriceps-strengthening equipment. When the seat was at 90 degrees, perpendicular to the floor, exercisers reduced the risk of straining their lower backs and actually targeted their quadriceps better than when the seat was set at a greater angle. Besides squats, "the leg-extension machine is one of the best ways to isolate the quadriceps," says Joseph F. Signorile, study coauthor at the University of Miami.